R - converting date and time fields to POSIXct with HHMMSS format

Question

I have a data file which has three columns thus:

20010101 000000  0.833
20010101 000500  0.814
20010101 001000  0.794
20010101 001500  0.772
...

Answer 1

Simply you can use lubridate package which is super awesome and fast. for your purpose try this:

df <- read.table(text="20010101 000000  0.833
20010101 000500  0.814
20010101 001000  0.794
20010101 001500  0.772", 
                  header=FALSE, colClasses=c("character", "character",     "numeric"), 
                  col.names=c("Date", "Time", "Val"))

df$mix <- paste(df$Date, df$Time)
df$mix <- parse_date_time(df$mix, 'Ymd HMS')

Just you have to feed the correct format to it. I prefer it to as.POSICct because it is much more flexible and you have other functions to work with time variables.